ROME, Italy — With a swing of her hip, the soprano Francesca Dotto swept up a makeshift wooden staircase in a rehearsal space in Teatro Nazionale in Rome, only to have her long train get caught in one of the steps.

There was a low murmur from the side of the audience where the designer Valentino Garavani was watching the partial run-through of Verdi’s “La Traviata,” sitting next to his longtime business partner, Giancarlo Giammetti, and the current creative directors of Maison Valentino, Maria Grazia Chiuri and Pierpaolo Piccoli.

“Hmmm, that’s a haute couture dress,” joked one of the press agents permanently affixed to the Valentino coterie, in past and present incarnations.

Actually, it was a simple white multilayered tulle slip that Ms. Dotto, who was singing the lead role of Violetta, had affixed over a pair of jeans, so she could get used to moving in a long train on a restricted stage.

But on Sunday, when Ms. Dotto performs in a preview performance at the nearby Teatro dell’Opera Di Roma, she will be wearing the real thing: an exquisite haute couture gown designed by Mr. Garavani that took 800 hours to make.

“She’s getting used to it, I can’t wait to see it up the real stairs,” said the film director Sofia Coppola, during a break in the rehearsal on a recent afternoon. Onstage, the staircase will be almost 20 feet high, to better showcase the gown’s shimmering green tail.

Ms. Coppola is making her opera directing debut in this production, which is widely regarded as a coup for the Teatro dell’Opera di Roma, gradually emerging from a period of financial and internal turmoil.

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Dresses for “La Traviata” characters: the white dress for Flora designed by Maria Grazia Chiuri and Pierpaolo Piccioli, the other dress for Violetta, designed by Valentino Garavani.CreditChris Warde-Jones for The New York Times

Mr. Garavani designed the four dresses worn by Violetta while Ms. Chiuri and Mr. Piccioli designed the costumes for the rest of the cast, including two haute couture gowns for the other female principal, Anna Malavasi, in the role of Flora.

Mr. Garavani and Mr. Giammetti have been deeply involved in the production, which will be the first cultural project of the foundation that bears their names. The costumes for the chorus and male leads were made by the opera theater’s in-house costume department, which also made replicas of Mr. Garavani’s gowns for the alternate cast, where Violetta is played by Maria Grazia Schiavo.

A friend of Ms. Coppola — the English production designer Nathan Crowley, also known for his fashion installations for museum exhibitions (and Batman films) — designed the sets, with Jader Bignamini, associate director of the Verdi Orchestra in Milan, as conductor.

“It was a fortuitous coming together of people that sometimes just happens,” said Carlo Fuortes, the general manager of the Rome Opera House Foundation, who added that he had approached Ms. Coppola a few years ago to direct Mozart’s “Cosi Fan Tutte” for another theater but she wasn’t available.

The 15-performance run of “La Traviata” is already nearly sold out. “It is already the biggest box office hit in the history of the theater from 1880,” Mr. Fourtes said.

Elegance and beauty are the dominant leitmotifs of this edition of “La Traviata,” an opera based on “La Dame aux Camélias” by Alexandre Dumas, fils, that is a constant in theater repertoires everywhere, reinvented in countless enactments, from minimalist to modern to full-on mid-19th-century period pieces.

“We wanted to do a new production, a modern production, but modern as concept without being avant-garde,” said Mr. Giammetti, who with Mr. Garavani has been sitting in on most of the rehearsals, discreetly fussing over minutiae, including jewels, fans and hairdos. “It’s very traditional what we’re doing, but with an edge. That’s why we chose Sofia Coppola, who brings a modern vision.”

Marina Bianchi, Ms. Coppola’s assistant director, noted that it was “very unusual that a costume designer is so present.”

Ms. Coppola said, “When Valentino asked me, I thought, ‘I can’t say no,’” adding that she was reassured by the opera’s setting in Paris, where she lives “part of the time,” as well as her experience directing the period drama “Marie Antoinette” in 2006.

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At the Valentino atelier Rome, drafts for the dress, designed by Valentino Garavani, to be worn by the “La Traviata” character Violetta.CreditChris Warde-Jones for The New York Times

For “La Traviata,” however, she said: “I wanted to bring out the personal side of the French-courtesan, the party girl used to the social scene. It’s a very feminine world that I love.”

Mr. Garavani, who retired in 2008, returned to work (“I am hardly pensioned off, I am always doing something,” he said) to create Violetta’s gowns, a rare venture on the stage despite his much-avowed passion for theater.

It’s not his first foray with the footlights: Some 20 years ago he created the costumes for a short-lived opera on the life of Rudolph Valentino, and in more recent years he designed costumes for dancers of the Vienna State Opera Ballet and New York City Ballet. And it came as a relief that the female leads of “Traviata” were slim, the opposite of the sopranos of Mr. Garavani’s youth who “were often very large,” he said.

“I still have creativity inside,” he said. “Tomorrow I could do a runway show of 100 dresses with no problem.”

Ms. Chiuri and Mr. Piccioli had already crossed paths with the world of opera, collaborating with the set builders of the Teatro Dell’Opera Di Roma for their spring 2014 couture collection commemorating operatic heroines.

“Opera, like couture, is seen as something of the past, a little dusty, a little obsolete, instead it has to be rediscovered,” Ms. Chiuri said, and that is something that fashion can help to do.

Then, too, like couture, opera is replete with “artisans of great craftsmanship,” Mr. Piccioli and Ms. Chiuri agreed simultaneously. (At times, interviewing the duo is reminiscent of an operatic duet, the two riffing in tandem.)

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A work in progress for a “La Traviata” costume at the Valentino atelier in Rome.CreditChris Warde-Jones for The New York Times

The challenge in designing the costumes for Ms. Malavasi and the female chorus — a soft palette counterpoint to Violetta, reflecting the increasing moodiness of the drama — was to “preserve the sense of lightness that for us is a prerogative,” and make it work under the harsh lights of the stage, Ms. Chiuri said.

“We sought to create a big picture as though it were a painting,” Mr. Piccioli said, “because in the end what is impressive about opera is the grandiosity of the stage, so we wanted to dress all these people on the stage as if they part of one whole.”

Small touches — substituting a smoking jacket for the hunting jacket Alfredo Germont, Violetta’s lover, conventionally wears in the second act — were meant to underline Ms. Coppola’s intimate take on the opera.

“From the first meeting, we concurred on the spirit and the approach with respect to the opera,” Mr. Piccioli said. “With designers and a film director, we could have transformed the opera into something else. Instead we opted to be more subtle, seeking emotions rather than any big effect. We wanted to make this opera personal.”

“Bringing our own experiences, building on the matrix of a classical opera,” Ms. Chiuri chimed in.

For the singers, wearing haute couture has been realizing “every woman’s dream,” said Ms. Malavasi, who joked that as a mezzo-soprano she usually plays scrappily dressed Gypsies. Wearing Maison Valentino was “thrilling, like donning a work of art,” she said. Ms. Dotto said she felt a strong responsibility to wear her dresses “with nonchalance, with elegance,” and was grateful that Mr. Garavani and Mr. Giammetti had been very hands-on during rehearsals, ensuring that the dresses “made me feel good.”

“This is not a runway show,” she said. “It’s important that the dress be beautiful, but also functional to the action.” Nevertheless, she remained a “bit terrorized” that something could happen to the gowns, “especially in the scenes where I fall,” Ms. Dotto said.